The "Straight Dough" and the "Pre-Ferment" methods are two major conventional methods for the manufacture of yeast raised bread products.
For the Straight Dough method, all of the flour, water or other liquid, and other ingredients which may include, but are not limited to yeast, grains, salt, shortening, sugar, yeast nutrients, dough conditioners, and preservatives are blended to form a dough and are mixed to partial or full development. The resulting dough is allowed to ferment for a period of time ranging from 0 to 6 hours or more depending upon specific process or desired end-product characteristics. For example, "no-time" processing may call for virtually no fermentation time, or just enough time to convey the dough mass to the next processing stage. "Short-time" processing may require a somewhat longer fermentation (i.e., 10-60 minutes). "Long-time" processing may require fermentation times over 60 minutes to achieve desired results.
The next step in the process is the mechanical or manual division of the dough into appropriate size pieces of sufficient weight to ensure achieving the targeted net weight after baking, cooling, and slicing. Some systems, particularly common with roll production, call for a continuous degassing step and possibly final developing step immediately prior to dividing. The dough pieces are often then rounded and allowed to rest (Intermediate Proof) for varying lengths of time. This allows the dough to "relax" prior to sheeting and molding preparations. The time generally ranges from 5-15 minutes, but may vary considerably depending on specific processing requirements and formulations.
The dough pieces are then mechanically or manually formed into an appropriate shape. This is often accomplished by passing the dough through one or more sets of sheeting rolls to flatten the dough piece, followed by a curling operation to form an elongated dough cylinder. Numerous variations of the molding operation exist. In some cases, doughs are processed through "string" lines in which long dough cylinders are then cut into portions which later become roll products. For pan bread, the molded dough pieces are transferred into greased pans. In the case of hearth bread, the dough pieces may be transferred onto screens, pans, sheets, or other appliances for further processing. The dough pieces are then given a final "proof" prior to baking. The times vary widely depending on process and desired finished product. Times may range from zero to several hours. Typical ranges for most wholesale pan bread and rolls is 40 to 60 minutes, 90.degree.-100.degree. F., and 85-95% relative humidity.
The dough pieces are then baked at various times, temperatures, and steam conditions in order to achieve the desired end product. Loaves are then often cooled for up to an hour or more prior to slicing (if desired) and packaging.
In the Pre-Ferment method, yeast is combined with other ingredients and allowed to ferment for varying lengths of time prior to final mixing of the bread or roll dough. Baker's terms for these systems include "Water Brew", "Liquid Ferment", "Liquid Sponge", and "Sponge/Dough". A percentage of flour ranging from 0-100% is combined with the other ingredients which may include but are not limited to water, yeast, yeast nutrients and dough conditioners and allowed to ferment under controlled or ambient conditions for a period of time. Typical times range from 1-5 hours. The ferment may then be used as is, or chilled and stored in bulk tanks or troughs for later use. The remaining ingredients are added (flour, characterizing ingredients, additional additives, additional water, etc.) and the dough is mixed to partial or full development.
The dough is then allowed to ferment for varying lengths of time. Typically, as some fermentation has taken place prior to the addition of the remaining ingredients, the time required is minimal (i.e., 10-20 minutes), however, variations are seen depending upon equipment and product type. Following the second fermentation step, the dough is then treated as in the Straight Dough Method. As used herein the term "dough" or "dough mixture" describes a pliable mixture that minimally comprises a flour or meal and a liquid, such as milk or water.
As used herein the term "dough ingredient" may include, but is not exclusive of, any of the following ingredients: flour, water or other liquid, grain, yeast, sponge, salt, shortening, sugar, yeast nutrients, dough conditioners and preservatives.
As used herein, the term "baked good" includes but is not exclusive of all bread types, including yeast-leavened and chemically-leavened and white and variety breads and rolls, english muffins, cakes and cookies, confectionery coatings, crackers, doughnuts and other sweet pastry goods, pie and pizza crusts, pretzels, pita and other flat breads, tortillas, pasta products, and refrigerated and frozen dough products.
The use of enzymes to improve dough characteristics in baking is well known in the art. For example, amylases are used to hydrolyze the .alpha.-1,4-glycosidic linkages in polysaccharides, such as in starch granules. Alpha-amylases can attack long starch chains at random at their interior and can dextrinize and liquefy starch. The starch chains can then be further broken down by .beta.-amylase into maltose and maltotriose. The use of amylases provides maltose for enhanced yeast fermentation and induces changes in dough characteristics, such as a decrease in water absorption capacity, a slackening of the dough, and the development of stickiness.
Alpha-amylases also exert an indirect effect on crust color by releasing sugar during the early stages of baking which causes crust browning. Alpha-amylase also brings about starch dextrinization during the early stages of baking, which results in an improved grain and a softer texture.
Alpha-amylases are endoglycosidases which are reactive with specific internal linkages within an oligo- or polysaccharide substrate. Such endoglycosidases are referred to herein as Type I endoglycosidases. Additional Type I endoglycosidases that have also been used in baking are cellulase, glucoamylase and pentosanase (also known as hemicellulase or arabinoxylanase).
Proteases have also been employed in baking to impart dough mellowing effects. Fungal proteases can be added to the sponge to allow the enzyme to act on flour proteins during the fermentation period that permits a reduction in dough mixing time, improved machinability, faster proofing due to better gas retention, and in loaves with better symmetry and improved grain and texture characteristics. Baking Science and Technology, Vol. 1 , Pyler, E. J., Siebel Publishing Co., Chicago, Ill., pp. 132-182 (1988).
Other enzymes used in the baking industry include oxidoreductases such as lipoxygenase which catalyzes the coupled oxidation of carotene pigments of flour (thereby bleaching them) and of unsaturated fatty acids by atmospheric oxygen. The enzyme is used extensively by bakers to improve the whiteness of crumb color of bread. Pyler, et al. supra at p. 165; . Sumner, J. B., and Sumner, R. J., J. Biol. Chem. 134, 531 (1940).
As the demand for "natural foods" increases, the baking industry is searching for methods perceived as "natural" to obtain the softness, texture, whiteness and shelf-life characteristics of bread previously achieved by the use of additives such as emulsifiers, and other additives such as potassium bromate which is used as an oxidant for bread. Potassium bromate is used extensively as an improver for bakery flour. Bread bakers add it directly as a powder or tablet, or they may use it indirectly as an ingredient in yeast food and dough conditioners. Most of the bread produced in North America today has potassium bromate added in one form or another. Potassium bromate has several disadvantages in that when combined with combustible materials such as wheat flour, oil and grease it forms a highly flammable mixture that can ignite and explode if confined. In addition, ingestion of high levels of potassium bromate have been found to cause acute stomach cramps. Food Chemical News, p. 10, Jun. 1, 1989.
A "clean label" (i.e., a label free from ingredients viewed as "harmful chemicals" such as potassium bromate) is therefore highly desirable since the baking industry is searching for alternatives to the chemical additives they rely on currently. Enzymes are the natural additives that bakers will most likely turn to.
The use of enzymes that will impart better machinability characteristics to dough, such as better make-up performance (i.e., better dividing, rounding and molding characteristics), and will result in bread with finer and whiter crumb quality and softer texture, will be useful in the baking industry.
Type II endoglycosidases, as used herein, are a category of endoglycosidases which are capable of cleaving specific internal glycosidic linkages found in glycoproteins. These endoglycosidases cleave all or part of the carbohydrate moiety from a glycoprotein depending on the location of the reactive glycosidic linkage in the glycoprotein. Examples of Type II endoglycosidases include endo-.beta.-N-acetylglucosaminidases (Endo-D, Endo-H, Endo-L, Endo-CI, Endo-CII, Endo-F-Gal type and Endo-F) endo-.alpha.-N-acetylgalactosaminidase, endo-.beta.-N-galactosidases, peptide-N-(N-acetyl-.beta.-glucosaminyl) aspergine amidase F (PNGaseF EC 3.5 1.52) and glycopeptide N-glycosidase (Peptide N-glycosidase EC 3.2.2.18). See, e.g., Tarentino, A. L., et al. Biochem 24, 4665-4671 (1985); Arakawa, M., et al., J. Biochem., 76, 307-317 (1974); Plummer, T. H. et al., J. Biochem. 59, 10700-10704 (1984); Tarentino, A. L. et al., Biochem and Biophys. Res. Comm. 67, 455-462 (1975); Trimble, R. B. et al. Anal. Biochem. 141, 515-522 (1984); Tarentino, A. L., et al., Methods in Enzymology, 138, 770-778 (1987); Plummer, T.H., et al., J. Biol. Chem., 256, 10243-10246 (1981); and "Glycoprotein and Proteoglycan Techniques" by J. G. Beeley, Chap. 6, pp. 153-300, Elsevier, Amsterdam, New York, Oxford (1985). In addition to having a specificity for the internal glycosidic linkages of glycoproteins, at least one endoglycosidase (endo-.beta.-N-acetylglucosaminidase H, i.e., Endo-H) has also demonstrated a specificity which produces the cleavage of lipid-linked oligosaccharides (Chalifour, R .J. et al. Archives of Biochem. and Biophys. 229, 386-394 (1983)) and reportedly di-N-acetylchitobiose linkages in oligosaccharides and glycoproteins (Tarentino, A. L. et al. J. Biol. Chem., 249, 811-817 (1974). Such Type II endoglycosidases, in general, have been used primarily for analytical purposes, e.g., the determination of protein or carbohydrate sequence and/or the structure and function of specific glycoproteins. See, e.g., Hsieh, P. et al. J. Biol. Chem., 258, 2555-2561 (1983); and Geyar, R. et al., Eur. J. Biochem., 143, 531-539 (1984).
Type II endoglycosidases, however, have not been used in baking to improve dough and baked goods.